ROOF:

An automobile roof or car top is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements.

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IMPORTANT TYPES OF ROOF RE-INFORCEMENTS:

• Front roof rail reinforcements
• Central roof rail reinforcements
• Bow roofs reinforcements
• Rear roof rail reinforcements

Design of Roof includes:

• Ditch Area
• Front Roof Rail
• Rear Roof Rail
• Bow Roof(1,2)

# Ditch Area:

A roof ditch area extending in a generally longitudinal direction of a vehicle is fixedly coupled to a body member and form a longitudinal water management channel on a lateral side portion of a roof of the vehicle. It is a styling orient part, so it is produce inhouse only.

Ditch area may or may not having emboss at top (which may vary car to car depending on strength requirement). Minimum thickness of 0.75 I take for Roof in my design.

# Front Roof Rail:

• It is a additional part, which will act as a reinforcement for the roof front.
• While designing this part, we have to consider the visibility criteria and also space nesscary for mounting windshield glass, rubber around glass, rubber paste, sealant.
• This part made from body side outer scrap material.
• Minimum thickness required are 0.75mm
• This part may having emboss to provide strength

# Rear Roof Rail:

• It is also an additional reinforcement part, which is placed in rear end of roof.
• While designing this part we have to consider rear head room clearance and rear visibility criteria.
• Rear head room clearance is minimum 80mm, which depends on car to car and region to region.
• This part also having contact with outer body side.
• Minimum thickness I had given is 0.75mm.

# Bow Roof:

• The bow roof, which is placed under the roof to provide strength to the roof.
• Number of roof placed depends upon the length of car, there may be more than one bow roof placed under roof.
• It have a mastic point, which is used to make attached to the roof without any spot weld. This mastic seal influence over 60 to 80mm around it.
• Bow roof can be placed by two methods. One method of placing bow roof between front and rear roof rail and reinforcement center or it is placed on most flatten surface in roof.
• This flatten surface can be find by two methods depends on heat and snow condition.

# ANALYSIS ON THE FOLLOWING ROOF DESIGN:

There are mainly two type’s conditions that the roof needs to pass to hold the design criteria good, they are.

• Heat distortion condition
• Snow load condition

Heat distortion criteria :

Heat distortion criteria are nothing but the calculation used to find the distance between the bow roof reinforcements.

It is given by the condition: HOLDS GOOD<2.7mm

Predition Formula:

W = (1.73 × 10^-3× L)+ (1.85 × 10^-8 × R²/t) +( 1.10 × 10^-3 × I)- 2.68

Where,

L= ROOF length in x-direction

R= ROOF curvature

Where R= 2( R_x×R_Y)/(R_X+R_Y)

R_X= X curvature

R_Y= Y curvature

t= Roof plate thickness (mm)

I= BOW Roof span (mm)

Here is the table for heat distortion condition:

(ALL ARE IN MM)

NOTE:

The first data(No 1) considered ie. Between the front roof rail and central roof rail the Rx and Ry values are zero because of the presence of sun roof cut out.

The second data(No 2) the bow roof 1 is present within the central roof rail, hence the bow span is considered as zero. This is done to provide additional support to the roof due to the presence of sun roof

Obtained value are less than 2.7, So the heat distortion condition can be statified for the placed bow roof.